Device for enhancing the emptying of an inhaler metering chamber

ABSTRACT

A device is provided for emptying a metering chamber of a powder dispenser. The dispenser includes an expulsion channel passing through the metering chamber and a device for delivering an air flow which is intended to pass along the expulsion channel to empty the metering chamber when the dispenser is actuated. A flow device is adapted to configure the air flow in such a manner that it empties the metering chamber completely. The flow device is disposed in the expulsion channel upstream from the metering chamber in the flow direction of the air flow.

The present invention relates to a device for making it easier to emptya metering chamber of a powder dispenser, and in particular of a powderinhaler.

The use of powder inhalers is now widespread, particularly in thepharmaceutical field, and requirements concerning performance,efficiency, and manufacturing cost has become very tight.

One of the main requirements is to guarantee the best possiblereproducibility of the quantity of substance that is dispensed each timethe inhaler is actuated. This is particularly crucial when the inhalercontains medication that must be dosed very accurately, as isparticularly the case for medication against asthma.

Also, the quality of pulverization is likewise important in ensuringthat the expelled dose of powder does not include any clumps of powder.Such clumps prevent the powder from diffusing properly in the lungs andconsequently reduce the effectiveness of the product.

In general, powder inhalers comprise a metering chamber filled withpowder, which metering chamber is emptied when the inhaler is actuated,either by a flow of compressed air, or else by a flow of air generatedby the user inhaling. An example of one such known apparatus isdisclosed, in particular, in document WO 93/18812, and is shown in partin FIGS. 1 to 3. FIGS. 1 to 3 are respectively a longitudinal section, across-section, and a horizontal section of a metering chamber 10 havingan expulsion channel 20 passing therethrough extending to a mouthpiece30 of the dispenser. The metering chamber 10 is filled with substancefrom a supply of the substance (not shown), and when the apparatus is inoperation, a flow of air represented diagrammatically by arrows in FIGS.1 and 3, passes along said expulsion channel 20 to empty the meteringchamber 10 and bring the dose of substance to the mouthpiece 30 of thedispenser from which it is dispensed to the user.

To obtain good dose reproducibility, it is necessary both for themetering chamber to be refilled completely after each utilization, andalso for it to be emptied completely each time the apparatus isactuated. If the metering chamber is not emptied completely, then thevolume of the dose as expelled no longer corresponds to the prescribeddose, and the powder remaining in the metering chamber can form powderbuild-up zones that prevent good dose reproducibility.

In such an apparatus, expulsion of the powder dose, i.e. emptying of themetering chamber, is an operation that is very difficult to perform, andit depends on numerous parameters, including:

the shape and the size of the metering chamber, and thus the quantity ofmedication to be dispensed;

the shape of the expulsion duct, which often does not correspond to theshape of the metering chamber; thus, as can be seen in particular inFIG. 2, the metering chamber 10 is generally of cross-sectional areathat is greater than that of the expulsion channel 20;

the size of the expulsion duct, which needs to guarantee an appropriateair speed; and

the air flow conditions which depend on the source of air and on thedimensions of the expulsion duct.

In known devices, as shown in FIGS. 1 to 3, the expulsion duct 20 isgenerally cylindrical, and the air flow matches the shape of the duct.Thus, when the air flow penetrates into the metering chamber 10 while itis filled with powder, the flow follows a trajectory that issubstantially rectilinear between the inlet and the outlet of saidmetering chamber. Under such circumstances, particularly when themetering chamber is of large volume, the flow of air tends, initially,to "dig a tunnel" through the powder, i.e. to form a passage as shown indashed lines in FIG. 3 extending directly from the inlet to the outletof the metering chamber 10, with said passage correspondingsubstantially to an extension of the expulsion channel 20 through themetering chamber. In this way, only a portion of the powder contained inthe metering chamber is expelled. Thereafter, in a second step, if themetering chamber is not too large, the air flow entrains powder situatedaround said "tunnel".

Although that arrangement has been found to be effective for meteringchambers that are relatively small, it suffers from considerabledrawbacks when large doses are to be delivered. Under suchcircumstances, a portion of the powder lying in side zones of themetering chamber, i.e. zones in the vicinity of its walls, is notexpelled and builds up in said chamber, thereby giving rise to problemsof dose reproducibility.

As a result, increasing the volume of the metering chamber in such aprior art inhaler requires a corresponding adaptation of the expulsionchannel and thus of the air flow source, thereby considerably increasingthe cost of manufacturing such an apparatus.

In another known device, disclosed in document WO 95/28980, the meteringchamber is defined in part by an insert that projects into the expulsionchannel. That metering chamber also includes side zones that aredifficult to empty. Furthermore, because of the presence of the insertprojecting into the channel through a wall thereof, problems of powderretention can arise on the downstream portion of the insert, such thatdose reproducibility is not guaranteed.

An object of the invention is to provide a device that makes it easierto empty a metering chamber for the purpose of accurately guaranteeingdose reproducibility.

Another object of the invention is to provide a device for making iteasier to empty a metering chamber, in which the dose of powder iscompletely broken up while it is being expelled.

Documents U.S. Pat. No. 1,732,566 and U.S. Pat. No. 3,522,659 disclosedevices including flow means for modifying the configuration of the airflow in the metering chamber in order to facilitate emptying. The meansare disposed in the metering chamber in such a manner that modifying thedimensions of the metering chamber requires said flow means to bemodified.

Thus, another object of the invention is to provide a device making iteasier to empty a metering chamber in which it is possible to modify thevolume of the metering chamber without the need to modify any otherportion of the dispenser.

A further aim of the invention is to provide a device for making iteasier to empty a metering chamber, and that also makes it possible toguarantee good dose reproducibility, independently of the volume of themetering chamber, and without increasing the manufacturing cost of thedispenser.

The invention thus provides a device for making it easier to empty ametering chamber of a powder dispenser, said dispenser including anexpulsion channel passing through said metering chamber, and means fordelivering an air flow which is intended, when the dispenser isactuated, to pass along said expulsion channel to empty said meteringchamber, said device including flow means adapted to configure the airflow in such a manner that it empties said metering chamber completely,the device being characterized in that said flow means are disposed inthe expulsion channel outside and upstream from said metering chamber inthe flow direction of said air flow.

In particular, said metering chamber includes at least one portion ofcross-sectional area greater than the cross-sectional area of saidexpulsion channel, forming at least one side zone, said flow means beingadapted to direct at least a portion of the air flow into said at leastone side zone of said metering chamber in such a manner as to empty saidmetering chamber completely, including in said at least one side zone.

The invention is thus adapted to modify the configuration of the airflow as its penetrates into the metering chamber, and in particular insuch a manner that at least a portion of the air flow is directedtowards said side zones to expel the dose in full, independently of therelationship between the cross-sectional area of the metering chamberand that of the expulsion channel. It is thus possible to make inhalersusing metering chambers of various volumes and shapes without any needto modify other portions of the inhaler, which is of considerablyeconomic advantage. Also, dose reproducibility is guaranteed completelyin all of the various inhalers.

In a preferred embodiment of the invention, said flow means include aninsert disposed in fixed manner in said expulsion channel. Since theinsert is independent of the volume of the metering chamber, ittherefore guarantees that it is emptied regardless of its volume. Inparticular, a change in the volume of the metering chamber does notrequire a change of insert.

In a first variant, said insert includes a solid central core, the airflow flowing over the outside surface of said central core.

In a second variant, said insert includes a central core having an axialopening along its longitudinal central axis, a portion of the air flowflowing through said axial orifice and the remainder flows along theoutside surface of said central core.

In this way, the insert makes it possible to maintain the same air flowspeed while increasing the contact area between the air flow and thepowder contained in the metering chamber.

Preferably, said insert is dimensioned in such a manner as to be held infixed manner by being jammed in the expulsion channel. Whenmanufacturing an inhaler, it thus suffices to engage an insert of theinvention; in general the insert is a very cheap and small piece ofplastics or metal which is inserted into the expulsion channel upstreamfrom the metering chamber. No additional step is required to fix theinsert in the channel, where such a step would increase manufacturingcosts.

In a particular embodiment of the invention, the expulsion channel is ofcircular or oblong cross-section, and said insert is of polygonalcross-section.

In another particular embodiment of the invention, the expulsion channelis polygonal in section and said insert is of circular or oblongcross-section.

In a preferred embodiment of the invention, said insert further includesat least one rib extending substantially axially along the outsidesurface of said central core.

Advantageously, the expulsion channel is of substantially circularcross-section, the core of the insert being of substantially circularcross-section, smaller than that of said expulsion channel, said insertincluding a plurality of ribs extending substantially axially along theoutside surface of said central core, the outside diameter of the insertover said ribs being nearly identical to the inside diameter of saidexpulsion channel, such that the insert is held in said channel byjamming via said ribs.

Advantageously, the insert includes at least three ribs which areregularly distributed around the central core so that the central coreis centered in the middle of said expulsion channel.

Preferably, the insert includes four identical ribs that arediametrically opposite in pairs around said central core.

In a first variant, said at least one rib extends axially over thecentral core parallel to the longitudinal axis of the expulsion channel.

In a second variant, said at least one rib extends axially over thecentral core in twisting manner about the longitudinal axis of theexpulsion channel such that the insert establishes a turbulent air flow.

Preferably, the cross-section of the downstream end of said central coreof the insert in the flow direction of the air flow is greater than thecross-section of the upstream end of said central core such that theinsert establishes a flow of air that penetrates into the meteringchamber on a conical path.

Optionally, said flow means include at least one groove or rib extendinghelically along the inside wall of the expulsion channel. In thisvariant, the insert may optionally be omitted, with the helical profileformed in the expulsion channel establishing the turbulent flow of airin the metering chamber.

In yet another advantageous embodiment, said metering chamber is definedin part by a metering element disposed in fixed manner in the expulsionchannel, said metering element being disposed downstream from said flowmeans in the flow direction of said air flow.

Preferably, said metering element is disposed remotely from the walls ofthe expulsion channel in such a manner that the air flow flows over theentire periphery of said metering element. Thus, no powder can beretained on any portion of said metering element, and all of the dose isexpelled on each actuation.

Advantageously, said metering element is terminated in a point at itsdownstream end in the air flow direction.

Preferably, said metering element is fixed to said flow means.

Advantageously, said flow means are implemented in the form of an insertfixed to a fixing member, said fixing member being fixed axially in linewith the expulsion channel such that the insert projects into saidexpulsion channel away from the walls of said channel, the air flowflowing over the entire periphery of said insert. The insert may haveany of the shape described above, and in particular, said insert is ofrectangular cross-section and said metering element is of circularcross-section. Thus, the configuration of the air flow is modified bythe insert, and said modified air flow includes turbulence because ofthe shape of the insert, thereby causing the metering chamber to beemptied completely. Because the air flow flows all around the peripheryof the metering element, and because the metering element terminates ata point, it is guaranteed that the entire dose will be completelypulverized.

Preferably, said metering element, said insert, and said fixing memberare made as a single piece. This implementation facilitates installingthe device comprising the insert plus the metering element, and therebyreduces manufacturing and assembly costs. Also, in order to change themetering chamber, it suffices to change the metering element, withoutchanging any other part of the apparatus in any way, and that too limitscosts.

Advantageously, said metering element includes a zone, such as a cup,defining the volume of the metering chamber. Thus, to change the volumeof the metering chamber, it suffices to change said zone of the meteringelement, which can be done very simply and at low cost.

Advantageously, said air flow is a flow of compressed air created in thedispenser by a prestressed pump device which is triggerable duringactuation of the dispenser.

Other characteristics and advantages appear from the following detaileddescription given by way of non-limiting description and with referenceto the accompanying drawings, in which:

FIG. 1 is a diagrammatic longitudinal section view of a metering chamberand an expulsion channel of a prior art inhaler;

FIG. 2 is a cross-section view of the FIG. 1 arrangement;

FIG. 3 is a horizontal section of the FIG. 1 arrangement;

FIG. 4 is a view similar to that of FIG. 1, incorporating an insertconstituting a first embodiment of the invention;

FIG. 5 is a view similar to FIG. 2, incorporating the insert of FIG. 4;

FIG. 6a is a diagrammatic longitudinal section of an insert in anadvantageous embodiment of the invention;

FIG. 6b is a diagrammatic cross-section of the upstream end of the FIG.6a insert;

FIG. 6c is a diagrammatic cross-section of the downstream end of theFIG. 6a insert;

FIG. 7 is a view similar to FIG. 5 incorporating an insert constitutinga variant embodiment of the invention;

FIG. 8 is a view similar to FIG. 7, incorporating another variant insertof the invention;

FIG. 9 is a diagrammatic perspective view of an insert constitutinganother advantageous embodiment of the invention;

FIG. 10 is a diagrammatic view of a portion of a dispenser including theinsert of FIG. 9;

FIG. 11 is a view similar to FIG. 10, incorporating a deviceconstituting another embodiment of the invention; and

FIGS. 12a and 12b are diagrammatic cross-section views respectivelythrough the insert and through the metering element of the FIG. 11device.

With reference to FIG. 10, a dispenser such as a powder inhalercomprises a metering chamber 10 designed to be filled with substancefrom a supply 40 via a filling mechanism (not shown). The meteringchamber 10 has an expulsion channel 20 passing therethrough whichextends one way towards a dispensing mouthpiece 30 of the inhaler, andthe other way towards an air flow source (not shown). As can also beseen in FIG. 4, the invention provides for placing flow means such as aninsert 100 in the expulsion channel 20 upstream from the meteringchamber 10 in the air flow direction as represented diagrammatically bythe arrows, which flow means are designed to improve emptying of themetering chamber when the dispenser is actuated. The insert 100 which ispreferably fixed by being jammed in said expulsion channel 20, isdesigned to change the configuration of the air flow, and in particularits shape, as it penetrates into the metering chamber 10, and to do soin such a manner that said air flow is directed towards the side zones11 of the metering chamber 10 lying outside the portion of the expulsionduct 20 which passes through said metering chamber 10. As can be seen inparticular in FIGS. 4, 5, 7, and 8, the cross-section of the meteringchamber 10 is generally of greater area than is the cross-section of theexpulsion channel 20, so said side zones 11 are consequently portions ofthe metering chamber 10 that are situated in the vicinity of its sides.The insert 100 also makes it possible to establish turbulence orswirling in the air flow such that on penetrating into the meteringchamber, the turbulence or swirling acts to break up the dose of powder,should that be necessary. In this way, the entire dose is expelled inoptimum manner.

In accordance with the invention, the insert 100 comprises a centralcore 110 which extends preferably up to the entrance of said meteringchamber 10. In a preferred embodiment of the invention, the expulsionchannel and the central core 110 of the insert 100 are both ofsubstantially circular cross-section, with the cross-section of thecentral core naturally being slightly smaller than the cross-section ofsaid expulsion channel 20. The insert 100 is thus generally roughlycylindrical in shape. Preferably, the insert 100 also includes at leastone rib 115 extending approximately axially along the outside surface111 of said central core 110 of the insert 100. Advantageously, theinsert includes at least three ribs 115 distributed around said centralcore 110, said ribs being made in such a manner that the outsidediameter of the insert 100, over the ribs 115 is about the same or veryslightly greater than the inside diameter of said expulsion channel 20,thereby making it possible to fix the insert 100 in the channel 20 byjamming via said ribs 115. With reference to FIGS. 4 and 5, the insert100 has four identical ribs 115 extending parallel to the longitudinalaxis of the insert. These ribs 115 are diametrically opposite in pairsabout the central core 110 so that said central core 110 is centered inthe middle of said expulsion channel 20. In this example, the centralcore 110 is solid so that the flow of air coming from the air flowsource flows over the outside surface 111 of the central core 110 of theinsert 100 between the various ribs 115.

In this way, the shape of the air flow which was substantiallycylindrical prior to coming into contact with the insert 100, i.e. whichmatched the shape of the expulsion channel 20, is modified by the insert100 so that when the air flow opens out into the metering chamber 10, itis substantially in the form of a hollow tube such that the activeportion of the air flow is closer to the walls of the metering chamber10 and is not directed directly towards the outlet of said meteringchamber 10.

In an advantageous embodiment, shown in FIGS. 6a, 6b, and 6c, the insert100 of generally cylindrical shape comprises a central core 110 whosecross-section at its upstream end 110b in the flow direction of the airflow, is smaller than its cross-section at its downstream end 110a. Inthis way, the air flow flowing along the outside surface 111 of thecentral core 110 of the insert 100 penetrates the metering chamber 10with an air flow shape that is approximately frustoconical, flaringoutwardly, such that said air flow is directed even more stronglytowards the side zones 11 of the metering chamber 10 when it penetratestherein.

Another advantageous variant embodiment is shown in FIG. 9. As before,the insert 100, which is still generally cylindrical in shape, includesa central core 110 and four ribs 115 extending along its outside surface111. In this variant, said ribs 115 extend over said outside surface 110of the central core 110 in a manner that twists around the longitudinalaxis of the central core 110 of the insert, which corresponds to thecentral longitudinal axis of the expulsion channel 20. In this way, theair flow flowing along said outside surface 111 of the central core 110,between the ribs 115, penetrates into the metering chamber with aswirling motion, thereby emptying it much more thoroughly. This is thevariant of the insert 100 which is shown diagrammatically in the overallview of FIG. 10.

With reference to FIGS. 7 and 8, other variants of said insert 100 areshown diagrammatically. In this way, said central core 110 need not haveribs 115. In which case, if the expulsion channel 20 is of circularcross-section, the cross-section of the insert can be polygonal,preferably square or rectangular, so that it can be jammed in saidexpulsion channel 20 via its corners. As before, the air flow flowsalong the outside surface 111 of said central core 110. As shown in FIG.8, said core 110 may also include an axial opening 112 extending alongits central longitudinal axis, so that the air flow which reaches saidinsert 100 separates into a portion that flows axially through saidaxial opening 112, and a portion which flows over the outside surface111 of said central core 110. When, as shown in FIGS. 7 and 8, theexpulsion channel 20 is of circular cross-section and the insert 100 hasa central core of rectangular cross-section, it is possible to changethe distribution of the air flow over the four faces of said centralcore of generally rectangular shape, as a function of the shape of themetering chamber 10. Thus, when the metering chamber 10 is deeper thanit is wide (FIG. 7), it is advantageous for the long sides of the insert100 to extend horizontally, to deliver the larger portion of the airflow towards the top and bottom walls of the metering chamber 10. Incontrast, when the metering chamber is wider than it is deep (FIG. 8),then the long sides of the rectangular parallelepiped 110 areadvantageously disposed vertically so as to deliver the greatest portionof the air flow towards the side walls of the metering chamber 10.Naturally, any other polygonal shape for the cross-section of the insert100 could be envisaged for obtaining the desired result, i.e. completeemptying of the metering chamber 10 by the air flow issued when theinhaler apparatus is actuated.

The various embodiments of the insert have been described with referenceto an expulsion channel of cross-section that is substantially circular,however they can be applied equally to an expulsion channel ofcross-section that is elliptical or oblong. Similarly, an expulsionchannel of polygonal cross-section (in particular a section that isrectangular or square) can receive an insert in accordance with any oneof the above-described embodiments of the invention. Also, if referenceis made to the embodiments shown in FIGS. 7 and 8, the respective shapesof the cross-sections of the channel 20 and of the insert 100 can beinterchanged, i.e. the expulsion channel 20 could be rectangular incross-section, in which the case the insert 100 advantageously has acentral core 110 of cross-section that is circular or elliptical.

Optionally, provision can be made for one or more grooves or ribs toextend helically along the inside wall of the expulsion channel. Inwhich case, a portion of the air flow flows along said grooves or ribsso that a spinning air flow is created in the metering chamber. This canenable the insert to be omitted.

In another preferred embodiment of the invention, as shown in FIGS. 11,12a, and 12b, the metering chamber 10 is partially defined by a meteringelement 200, in particular by means of a zone that defines the volume ofsaid metering chamber. The zone 210 can be made in the form of a cup, asshown in FIGS. 11 and 12b, however it could equally well be arbitrary inshape, e.g. in the form of a mere flat supporting the quantity of powderthat is fed from the supply 40. In accordance with the invention, saidmetering element 200 is fixed in the expulsion channel 20, downstreamfrom said insert 100. The metering element 200 is preferably fixed inthe expulsion channel 20 at a distance from the walls of said channel sothat the air flow flows over its entire periphery. In this way, the airflow expels all of the powder since no powder retention can occuragainst a portion of said metering element 200. For even greaterimprovement thereof, the downstream end 220 of the metering element 200advantageously terminates in a point.

Preferably, as shown in FIG. 11, the metering element 200 is fixed tothe element 100, which is itself advantageously fixed to a fixing member300. This fixing member 300 is fixed on the axis 20b of the expulsionchannel 20, e.g. by jamming or by anchoring. Thus, the insert 100 andthe metering element 200 project axially into the expulsion channel 20.The insert 100 is preferably also disposed remotely from the walls ofthe channel 20 so that the air flow flows around the entire periphery ofthe insert 100. In an advantageously embodiment of the invention, thefixing member 300, the insert 100, and the metering element 200 are madeas a single piece, preferably of plastics material. Manufacture andassembly of the device of the invention are thus made very simple andtherefore of very low cost, and a modification to the metering chamber,e.g. of its volume, can be implemented very easily while modifying onlysaid metering element 200.

Preferably, as shown in FIGS. 12a and 12b, the cross-section of theinsert 100 is substantially rectangular, while that of the meteringelement 200 is substantially circular. Thus, the insert 100 changes theconfiguration of the air flow and the transition between the insert andthe metering element 200 therefore further enhances the creation ofturbulence, such that it is guaranteed that the entire quantity ofpowder will be expelled in finely-divided form.

The various characteristics described above with reference to thevarious embodiments of the invention can Naturally be combined with oneanother in any manner without going beyond the ambit of the invention.

We claim:
 1. A powder dispenser comprising:a metering chamber (10); anexpulsion channel (20) passing through said metering chamber (10); andmeans for delivering an air flow intended, when the dispenser isactuated, to pass along said expulsion channel (20) to empty saidmetering chamber (10), flowing means (100) adapted to configure the airflow in such a manner that it empties said metering chamber (10)completely, and wherein said flowing means (100) is disposed in theexpulsion channel (20) outside and upstream from said metering chamber(10) in the flow direction of said air flow, wherein said flowing meansis independent of the dimensions of said metering chamber, wherein saidmetering chamber (10) includes at least one portion of cross-sectionalarea greater than the cross-sectional area of said expulsion channel(20), forming at least one side zone (11), said flowing means (100)being adapted to direct at least a portion of the air flow into said atleast one side zone (11) of said metering chamber (10) in such a manneras to empty said metering chamber (10) completely including in said atleast one side zone.
 2. A powder dispenser according to claim 1, inwhich said flowing means (100) include an insert (100) disposed in afixed manner in said expulsion channel.
 3. A powder dispenser accordingto claim 2, in which said insert (100) includes a solid central core(110), the air flow flowing over an outside surface (111) of saidcentral core (110).
 4. A device according to claim 2, in which saidinsert (100) includes a central core (110) having an axial opening (112)along its longitudinal central axis, a portion of the air flow flowingthrough said axial opening (112) and the remainder flows along anoutside surface (111) of said central core (110).
 5. A powder dispenseraccording to claim 2, in which said insert (100) is dimensioned in sucha manner as to be held in fixed manner by being jammed in the expulsionchannel (20).
 6. A powder dispenser according to claim 2, in which theexpulsion channel (20) is of circular or oblong cross-section, and saidinsert (100) is of polygonal cross-section.
 7. A powder dispenseraccording to claim 2, in which the expulsion channel (20) is polygonalin section and said insert (100) is of circular or oblong cross-section.8. A powder dispenser according to claim 2, in which said insert (100)further includes at least one rib (115) extending substantially axiallyalong an outside surface (111) of a central core (110).
 9. A powderdispenser according to claim 8, which the expulsion channel (20) is ofsubstantially circular cross-section, the core (110) of the insert (100)being of substantially circular cross-section, smaller than that of saidexpulsion channel (20), said insert (100) including a plurality of ribs(115) extending substantially axially along the outside surface (111) ofsaid central core (110), the outside diameter of the insert (100) oversaid ribs (115) being nearly identical to the inside diameter of saidexpulsion channel (20), such that the insert (100) is held in saidchannel (20) by jamming via said ribs (115).
 10. A powder dispenseraccording to claim 8, in which the insert (100) includes at least threeribs (115) which are regularly distributed around the central core (110)so that the central core (110) is centered in the middle of saidexpulsion channel (20).
 11. A powder dispenser according to claim 8, inwhich the insert (100) includes four identical ribs (115) that arediametrically opposite in pairs around said central core (110).
 12. Apowder dispenser according to claim 8, in which said at least one rib(115) extends axially over the central core (110) parallel to thelongitudinal axis of the expulsion channel (20).
 13. A powder dispenseraccording to claim 8, in which said at least one rib (115) extendsaxially over the central core (110) in a twisting manner about thelongitudinal axis of the expulsion channel (20) such that the insert(100) establishes a turbulent air flow in the metering chamber (10). 14.A powder dispenser according to claim 2, in which the cross-section ofthe downstream end (110a) of a central core (110) of the insert (100) inthe flow direction of the air flow is greater than the cross-section ofthe upstream end (110b) of said central core (110) such that the insert(100) establishes a flow of air that penetrates into the meteringchamber (10) on a conical path.
 15. A powder dispenser according toclaim 1, in which said flowing means (100) includes at least one grooveor rib extending helically along an inside wall of the expulsion channel(20).
 16. A powder dispenser according to claim 1, in which saidmetering chamber (10) is defined in part by a metering element (200)disposed in fixed manner in the expulsion channel (20), said meteringelement (200) being disposed downstream from said flowing means (100) inthe flow direction of said air flow.
 17. A powder dispenser according toclaim 16, in which said metering element (200) is disposed remotely fromthe walls of the expulsion channel (20) in such a manner that the airflow flows over the entire periphery of said metering element (200). 18.A powder dispenser according to claim 16, in which said metering element(200) is terminated in a point (220) at its downstream end in the airflow direction.
 19. A powder dispenser according to claim 16, in whichsaid metering element (200) is fixed to said flowing means (100).
 20. Apowder dispenser according to claim 19, in which said flowing means(100) are implemented in the form of an insert (100) fixed to a fixingmember (300), said fixing member (300) being fixed axially in line (20a)with the expulsion channel (20) such that the insert (100) projects intosaid expulsion channel (20) away from the walls of said channel (20),the air flow flowing over the entire periphery of said insert (100). 21.A powder dispenser according to claim 20, in which said insert (100) isof rectangular cross-section and said metering element (200) is ofcircular cross-section.
 22. A powder dispenser according to claim 20, inwhich said metering element (200), said insert (100), and said fixingmember (300) are made as a single piece.
 23. A powder dispenseraccording to claim 16, in which said metering element (200) includes azone (210), formed as a cup, defining the volume of the metering chamber(10).
 24. A powder dispenser according to claim 1, in which said airflow is a flow of compressed air created in the dispenser by aprestressed pump device which is triggerable during actuation of thedispenser.